linux-kernel - Re: printk meeting at LPC 2022

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Date:   Fri, 23 Sep 2022 08:16:09 -0700
From:   Linus Torvalds <torvalds@...uxfoundation.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helge Deller <deller@....de>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        John Kacur <jkacur@...hat.com>,
        "John B. Wyatt IV" <jbwyatt4@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: printk meeting at LPC 2022

On Fri, Sep 23, 2022 at 7:49 AM John Ogness <john.ogness@...utronix.de> wrote:
>
> - Printing the backlog is important! If some emergency situation occurs,
>   make sure the backlog gets printed.

Yeah, I really liked the notion of doing the oops with just filling
the back buffer but still getting it printed out if something goes
wrong in the middle.

That said, I'm sure we can tweak the exact "how much of the back log
we print" if there are any real life issues that look even remotely
like the demo did.

It's not like you couldn't do a "skipping lines" message if there are
thousands of old non-emergency lines in the back buffer, and
prioritize getting the recent ones out first.

I doubt it ends up being an issue in practice, but basically I wanted
to just pipe up and say that the exact details of how much of the back
buffer needs to be flushed first _could_ be tweaked if it ever does
come up as an issue.

                    Linus